Megaloblastic change is a feature of colonies derived from an early erythroid progenitor (BFU-E) stimulated by monocytes in culture.

The morphology of stained preparations of cells from human bone marrow and peripheral blood erythroid colonies cultured in methylcellulose, were examined by light microscopy. Although the morphology of 7 d erythroid colonies (CFU-E) was largely normoblastic, bone marrow and peripheral blood erythroid burst (BFU-E) showed a variable degree of megaloblastic and culture system and the deoxyuridine suppression test demonstrated active thymidine synthesis. Megaloblastic morphology was correlated with the growth induced by the addition of monocytes to erythroid progenitors. It was concluded that megaloblastosis was a feature of the erythroblasts derived from an early BFU-E which required monocytes for their development.

Changes in the erythrocytes of the developing opossum, Didelphia virginiana.

Changes in the erythrocyte population during postnatal development of the opossum have been studied. At birth, the red cells of the peripheral blood number less than 600,000/cmm and the characteristic erythrocyte is a large nucleated cell ('megaloblast'). These are rapidly replaced by smaller, nonnucleated cells. The results indicate that the yolk-sac period of blood formation is short and that the hepatic phase of hemopoiesis begins prior to birth. The data also suggest that megaloblasts in the opossum may be able to transform into megalocytes.

Scanning electron and light microscope correlation of individual human bone marrow cells before and after culture in nutrient agar.

This study was undertaken with the aim of identifying the different cell types found in human bone marrow by examining their surface morphology. In an attempt to obtain a homogeneous cell population, cells were both fractionated by discontinuous albumin density gradient centrifugation (DADGC) and selectively grown in nutrient agar. Both cell preparations underwent the critical point drying technique before examination under both the scanning electron microscope (SEM) and subsequently the light microscope (LM). When the SEM image of individual cells was compared with the corresponding LM image, it was not easy to identify the different cell types, because of the shrinkage and distortion that occurred during their preparation. The shrinkage observed under the SEM amounted to a 45% reduction in mean cell diameter. This shrinkage was confirmed by comparing the SEM and LM images of the same cell. Although shrinkage occurred throughout the dehydration sequence, critical point drying was responsible for a 25% reduction in mean cell diameter. Furthermore, direct observation under LM of fixed cells drying in air from ethanol, revealed visible contraction of the cell and distortion of the cell membrane. We assume that a similar morphological change occurred during critical point drying. We conclude that the shrinkage and distortion, caused by the dehydration process involved in SEM preparation, severely limit the value of a study of surface morphology by SEM in the identification of the different cell types found in human bone marrow.

Multinucleated erythroid cells in blood of golden hamster embryos. / Mnogoiadernye éritroidnye kletki v krovi émbrionov zolotistogo khomiaka.

Blood smears of 11 and 13-day-old embryos (20) and newborns (10) of golden hamsters were analysed. The smears were stained with brilliant cresyl blue in a moist chamber for 5--7 min. About 2--6 thousand cells were counted in 200 visual fields. By means of an ocular micrometer MOB-1 the diameters of 300 cells were measured and the curves on cell distribution were plotted according to the diameters. It was found that the blood of 11-day-old golden hamster embryos contained about 8% of binuclear and sixnuclear megaloblasts, and that of 13-day-old embryos--about 2.5% of binuclear and sixnuclear erythroblasts and megablasts of the second generation. In the bloood of newborn hamster polynuclear cells are absent.

Cytogenetic analysis of erythroleukaemia in two children - evidence of nonmalignant nature of erythron.

Serial cytogenetic and cytological studies in 2 cases of erythroleukaemia in children indicated that erythropoiesis is not involved in the malignant process itself, but represents a response caused by unknown stimuli. A good correlation was observed between the percentage of aneuploid cells and blasts in mitosis, thus during the erythroid phase aneuploidy was minimal or absent, while during the myeloblastic phase a high percentage of members of the aneuploid clone was present. An inverse correlation between peripheral normoblast count and haemoglobin level indicated that erythropoiesis was under physiological control. Taken together these observations constitute evidence that, in the cases of erythroleukaemia studied, erythroid cells do not have inherent malignant properties. Cytogenetic analysis offers a tool for differentiating this type of erythroleukaemia from other forms of DiGuglielmo's syndrome.

Oral contraceptive hormones, folate metabolism, and the cervical epithelium.

The currently available evidence concerning disorders of folate metabolism in women taking oral contraceptives has been reviewed. A disturbance in folate balance serious enough to cause symptoms (i.e., megaloblastic anemia) occurs very rarely. In some series, but not in others, serum and/or red cell folate concentrations have been reduced in oral contraceptive users. It is doubtful whether sex steroids affect polyglutamate folate absorption. About 20 percent of women taking contraceptive hormones manifest mild megaloblastic changes on Papanicolaou smears of the cervicovaginal epithelium which disappear after folic acid therapy. The current evidence, however, would not indicate that any significant benefit would ensue from routine folate supplementation in women on oral contraceptives.